Related technologies indicate that an eccentric portion of a rotary compressor has a cylindrical shape, a piston is fitted over an outer circumferential face of the eccentric portion, and an entire inner circumferential face of the piston is in contact with the entire outer circumferential face of the eccentric portion. When the eccentric portion drives the piston to rotate, a frictional loss occurs, so the eccentric portion is provided with an oil hole to improve lubrication between the eccentric portion and the piston.
However, during operation of the rotary compressor, the piston withstands a gas force due to a pressure differential between high and low pressure sides, and transmits the gas force to the eccentric portion through an oil film between the piston and the eccentric portion. The outer circumferential face of the eccentric portion bears different loads in different regions, and the position of the oil hole affects the oil film distribution and even degrades the bearing capacity of the oil film, resulting in abnormal abrasion. Furthermore, the frictional loss occurs when the eccentric portion drives the piston to rotate, thereby leading to an increase in workload of the rotary compressor.